∫ ( c o s x ) d x {\displaystyle \int (cos{\sqrt {x}})dx} = 2 x ∫ ( c o s u ) d u {\displaystyle 2{\sqrt {x}}\int (cosu)du} = 2 ∫ u ( c o s u ) d u {\displaystyle 2\int {u}(cosu)du}
u {\displaystyle {u}} = x {\displaystyle {\sqrt {x}}}
d u {\displaystyle {du}} = 1 2 x d x {\displaystyle {\frac {1}{2{\sqrt {x}}}}dx}
2 x d u {\displaystyle 2{\sqrt {x}}{du}} = d x {\displaystyle {dx}}
